Typical radio access cellular networks operate by way of various radio transmission devices, or base stations. These base stations provide wireless access to wireless mobile devices, such as cellular phones, to a core network of a cellular service provider. The base stations along with various data routing and control mechanisms (e.g., base station controllers, core and edge routers, and so on) facilitate remote communication for the mobile devices. As communication service providers expand base station coverage, more land areas can be covered by the radio access network. However, some areas can be difficult to provide reliable radio coverage, for various reasons such as population, high mobile traffic, interference with other transmitters, or materials that absorb base station transmission (e.g., dense, concrete and steel buildings, underground facilities, and the like).
Indoor cellular reception in particular has issues such as high interference, especially in higher floors subject to significant pilot signal noise pollution. Some venues have high capacity for people within a small area (e.g., shopping mall, airport terminal). These high density communication venues thus strain available capacity. It can be difficult to provide seamless integration of indoor cells with outdoor cells, not only managing interference but also in association, neighbor lists and call reselection procedures.
One solution to provide mobile communication support to areas where radio access is difficult, is a ‘personal’ base station, or femto Base Station (BS) (also termed, e.g., a home Node B or Femtocell). A BS can be a relatively small range device (compared with standard radio network base stations, such as a Node-B) that facilitates wireless communication over a licensed cellular radio band (as opposed to an unlicensed band, utilized by wireless local area network routers). In an exemplary aspect, the BS can be of any size to serve a large coverage area and amount of user equipment (e.g., cellular devices, mobile station, access terminals, handsets, etc.) within the coverage area. The BS can maintain a wireless link with cellular devices over such a radio band, in a similar manner as a Node-B base station. Consequently, a BS can provide small range cellular coverage for an area that does not receive a good signal from a radio access base station. Often, an individual consumer might utilize a BS in their home, an apartment building, an office building, and so on, for personal cellular access. In addition to mobile phone networks currently in place, a new class of small base stations has emerged, which may be installed in a user's home and provide indoor wireless coverage to mobile units using existing broadband Internet connections. Such personal miniature base stations are generally known as access point base stations, or, alternatively, Home Node B (HNB) or femtocells. Typically, such miniature base stations are connected to the Internet and the mobile operator's network via DSL router, IP communication or cable modem.
Conventionally, for a deployment model where femtocells are preferred because of a billing advantage or macro capacity off-load reason, it is often desirable that user equipment (UE) discovers and camps on its own femtocell when within its coverage area. More generally, UE can have a preference for a node based upon various considerations. For example, a service provider can offer better quality of service, additional services, etc. Thus, a preferred node can be a macro base station, femtocell.
By way of illustration, consider a conventional approach using standard non-HCS (Hierarchical Cell Structure) cell reselection rules. Periodically a neighbor search is performed, by all served mobile devices or UEs, depending upon the signal quality of a serving node. For example, a neighbor list search is triggered only when the signal strength of the current cell falls below certain thresholds e.g., a threshold SINTRASEARCH that triggers intra-frequency search and above a lower threshold SINTERSEARCH that triggers inter-frequency search). A femtocell or Home Node B (HNB) deployed in the midst of a strong macro cell would never be searched for and found, especially when the HNB is deployed on a different carrier frequency from the macro one that the mobile device or user equipment (UE) is camping on. Thus, the conventional approach does not provide for reliably discovering and camping on a preferred node.
Another known approach is using HCS (Hierarchical Cell Structure) cell reselection rules to make finding HNBs more likely, forcing all served mobile devices or UEs to search and measure high-priority base stations in all channel conditions and at all locations. A similar result can be achieved by elevating the non-HCS search thresholds resulting in a nearly continual search. Such continual searching can have significant impact on the standby time, reducing availability to the currently serving node and increasing power consumption. Moreover, many if not most of the served mobile devices or UEs may have no preferred node thus receiving no benefit for the increased power consumption.